Lifting tongs

ABSTRACT

This invention relates to lifting tongs embodying pivotally linked cross arms secured in a frame and having jaws which are constrained by the frame to open and close along a common rectilinear path in response to an overhead lift. This invention avoids the drawback associated with conventional tongs in which the tongs move along an arcuate path wherein the thickness of, say, a slab which can be gripped satisfactorily with a particular jaw-opening range is limited. Further, the design in accord with this invention enables a firm grip to be obtained over the whole jaw-opening range.

United States Patent Smith Oct. 17, 1972 [54] LIFTING TONGS v 3,397,907 8/1968 Trowbridge ..294/119 [72] Inventor: Henry Smith, Sheffield England 3,649,062 3/1972 Young, Jr. ..294/106 [73] Assignee: British Steel Corporation, London, Primary Examiner-Evon C. Blunk England Assistant Examiner-Douglas C. Bellis [22] Filed: July 16, 1971 Attorney-Bacon & Thomas [21] Appl. No.: 163,401 [57] ABSTRACT This invention relates to lifting tongs embodying [30] Foreign Application Priority Data pivotally linked cross arms secured in a frame and Au 4 1969 Great Britain 37 524/69 having jaws which are constrained by the frame to open and close along a common rectilinear path in response} to an overhead lift. This invention avoids the g drawback associated with conventional tongs in which [58] Fieid H5 104 the tongs move along an arcuate path wherein the 22 1 thickness of, say, a slab which can be gripped satisfac- I torily with a particular jaw-opening range is limited. 56 R f d Further, the design in accord with this invention ena- 1 e erences bles a firm grip to be obtained over the whole jaw- UNITED STATES PATENTS Opening Tange- 1,851,923 3/1932 McQuigg ..294/115 10 Claims, 3 Drawing Figures 22 i 21 29 I /l 1 28 27 26 I I I 39M -1 11.,36

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I Y 43 42 m w PATENTEDncI 11 1912 I 3,698,757

sum 1 or 2 INVENTOR HENRY SMI H .4 TTORNE Y5 PKTENTED 17 I972 3,698,757

SHEET 2 or 2 INVE/V r01? HENRY SM/TH :4 TTOANEYS LIFTING TONGS This invention relates to lifting tongs, e.g., tongs suitable for lifting and transporting loads such as steel slabs, billets, etc.

Hitherto, tongs designed for this purpose have frequently embodied crossed arms with or without a central fulcrum, the gripping action on the load being self-centering so that the load depends centrally from the tongs as it is lifted and transported. The drawback with tongs of this type, however, is that the remote ends of the arms on which the jaws are disposed move along arcuate paths so that the thickness of a slab which can be gripped satisfactorily with tongs having a particular jaw-opening range is limited. Further, the gripping force reduces quite substantially as the jaws move closer to one another so that the jaw-opening range is again restricted reducing the versatility of the tongs since several different ones need to be used to cover widely different slab widths.

It is an object of this invention to provide improved lifting tongs.

In accordance with this invention there is provided lifting tongs comprising two crossed arms each pivotally secured at one end in a frame and connected at their other ends to a common coupling, two crossed links pivotally secured at one end to each of the two arms at a position between the said one ends of these arms and the position at which they crossover, and having pivotally secured to their other ends jaws which are constrained by the frame to move along a common rectilinear path to grip a load between them in response to the coupling being lifted.

The coupling itself may include two further arms which are connected at one end to a common pivot point and are pivotally connected at their other ends to the said other ends of the crossed arms, a beam being operatively connected to this pivot point.

The tongs may be of the so-called duplex type in which two sets of the tongs, as defined, are connected together and spaced apart by a framework, the coupling beam, which is adapted to be raised and lowered by an overhead crane, being common to the two sets of tongs. With this arrangement long loads can readily be lifted and transported by reason of the widely spaced pick-up points.

Locking means may be embodied in the tongs so as automatically to lock them open after the coupling has been lowered and the load set down, and with duplex tongs these locking means may conveniently comprise a hooked mechanism secured to the beam and adapted to hook around the framework.

In order that the invention may be fully understood one embodiment thereof will now be described, by way of example with reference to the drawings; for convenience the embodiment illustrated is the duplex type tongs.

In the drawings:

FIG. 1 shows a side elevation of the tongs;

FIG. 2 shows a plan view of these tongs; and

FIG. 3 shows a sectional end elevation of FIG. 1 through A-A.

Referring now to the drawings two pairs of tongs l, 2 are mounted at opposite ends of a framework 3. A beam 4 which is dependent from an overhead crane (not shown) through chain shackles 5 extends through the framework and is coupled in common to the tongs.

The tongs themselves comprise a number of arms, which are described in more detail in FIG. 3, pivotally secured within frames 6, 7. These two frames have secured between them a central bar 8 and two rods 9, 10 V-shaped arms ll, 12 being welded between these members to strengthen this fabrication. The beam 4 extends through, and is welded to, apertured lugs 14, 15 on the frames 6, 7, respectively, and similar lugs 16 in the center of the framework.

These lugs 16 support a locking device comprising a frame 17 depending centrally of the beam and having a hooked end 18 which nestles around the underside of the bar 8 in the position illustrated. The action of this device will be described later in more detail.

Secured to the center of the beam is a saddle 19, this member merely serving as a support for the crane chain ring (not shown) when this is not in use.

The tongs themselves are better illustrated in FIG. 3 but in the figures under discussion some features of this item are visible, principally a central pivot pin 20 and arms 21 to 24.

Referring now to FIG. 3, which shows only one-half of thetongs at one end, the arms 21, 22 are pivotally secured to the pin 20 which, in turn, is secured between the apertured lugs 14. The outer ends of the arms are pivotally secured to cranked arms 23, 24 by pins 26, 27 which are accommodated in arcuate slots 28, 29 formed in the frame 6, the other ends of these arms being secured to pins 30, 31 in this frame.

As shown, the cranked arms cross over one another, and pivotally secured to these arms at positions between the cross-over point and theirlower ends are two links 32, 33, the other ends of these links being pivotally secured to jaws 34, 35 respectively. The links are secured to these cranked arms by pins 36, 37 which are accommodated in further arcuate slots 38, 39 in the frame, and are secured to the jaws by pins 40, 41 which are similarly accommodated in slots 42, 43, these slots, however, being straight and running horizontally. In addition, the jaws themselves are provided with pins 44, 45, which are also accommodated in these slots so as to constrain their attitude.

Both of the links 32 the other link (not shown) lies alongside the one illustrated nestle in a centrally formed slot 46 in the jaw 34 while the two links33 again only one is visible are secured in recesses 47 formed in the opposite sides of the jaw 35.

Finally, a spacer 48'is provided between the two arms 23, and spacers 49 are provided between the two arms 24 and the adjacent frame.

In describing the operation of the tongs it will be assumed that they are initially in the position shown, i.e., locked, with the jaws open in a position of rest.

The tongs are transported by crane to a loading bay in which, for example, a number of elongated steel slabs are stacked. The tongs are lowered over the uppermost slab so that it lies longitudinally between the jaws and the locking device is released by manually pulling the hooked end 18 of the frame 17 away from the underside of the bar 8. When the crane is now operated so as to lift the beam 4 the latter moves relatively to the bar 8, since the locking device is released, and the arms of the tongs move within the constraints imposed by the frame. In particular, with reference to FIG. 3, as the beam 4 is raised the arms 21, 22 are moved upwardly via the pin 20 and the cranked arms 23, 24 follow suit, the pins 26, 27 riding up the arcuate slots, 28, 29 respectively. The links 32, 33 which are secured to the cranked arms, move in sympathy with them, the pins 36, 37 secured to the upper ends of these links following arcuate paths defined by the slots 38, 39

while the pins 40, 41 secured to-their lower ends are constrained to move towards one another along the horizontal slots 42, 43. Thus the jaws 34, 35, to which the pins 40, 41 are also secured, move towards one another to grip the slab firmly between them.

I Once the slab is engaged in this manner there is practically no further relative movement between the arms which are now stressed as the beam is lifted so as to grip the slab more firmly as it is raised.

When the slab is deposited the beam is lowered and as the slab is set down continuing downward movement of the beam causes the arms of the tongs to relax towards the position shown whereupon the locking device automatically re-engages as the hooked end 18 rides over the bar 8 and nestles beneath its underside. Thus, when the beam is raised again the tongs ride clear of the deposited slab.

Although the invention has been described in relation to the particular embodiment illustrated it is to be understood that various modifications may be made without departing from the scope of this invention. For example, as already inferred, the principles employed are equally applicable to single tongs as to the duplex type shown. Further it is not necessary for two similar sets of arms, links, etc., to be provided at the tongs and one set or even more than two sets may alternatively be employed depending on the workload requirement.

The beam may also conveniently be utilized to sup port other items, e.g., chain retaining devices and pulleys for slab turnover devices, but these do not constitute part of this invention and in the interests of clarity they have not been illustrated.

We claim:

1. Lifting tongs comprising a frame,

a coupling on said frame,

two crossed arms each pivotally secured at one end in the frame and at their other ends to the coupling,

two crossed links pivotally secured at one end to each of the two arms at a position between the said one ends of these arms and the position at which they cross over, and

two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the coupling being lifted. 2. Lifting tongs according to claim 1, comprising two rectilinear guideways in said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways.

3. Lifting tongs according to claim 2, comprising two arcuate guideways in said frame, and wherein the links are pivotally secured to the two arms through pins which protrude into the frame and are accommodated in the said arcuate guideways.

4. Lifting tongs comprising a frame,

a beam,

a pair of first arms each connected at one end to said beam,

a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at theirother ends to the other ends of the first arms,

two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and

two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.

5. Lifting tongs according to claim 4, comprising two sets of arcuate guideways in said frame, and

a plurality of pins by which the second arms are pivotally secured (a) to the first arms and (b) to the crossed links, respectively, one set of guideways accommodating the pins effecting connection (a) and the other set of guideways accommodating the pins effecting connection (b),

a further set of guideways defining said rectilinear path, and

a pair of pins by which the crossed links are pivotally secured to the two jaws, the further set of guidewaysaccommodating the said pair of pins.

6. Lifting tongs comprising a frame,

a beam,

a pair of first arms each connected at one end to said beam, 1

a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms,

two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position,

two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted, and

locking means for automatically retaining the jaws of the tongs in an open posture after the beam has been lowered and the load set down.

7. Lifting tongs according to claim 6, wherein the first arms are connected to said beam through a common pivot.

8. A lifting tongs assembly comprising a framework, 1

two sets of lifting tongs mounted on and spaced apart by said framework, and

a beam common to the two sets of tongs, each one of said sets of tongs comprising a frame,

a pair of first arms each connected at one end to said beam,

a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms,

hooking around the framework after the beam has been lowered and the load set down whereby to constrain the jaws of the tongs to maintain their open posture, said mechanism being manually operable to unlock the jaws from their open posture. 10. A lifting tongs assembly according to claim 9, wherein each set of tongs comprises two rectilinear guideways in the said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways. 

1. Lifting tongs comprising a frame, a coupling on said frame, two crossed arms each pivotally secured at one end in the frame and at their other ends to the coupling, two crossed links pivotally secured at one end to each of the two arms at a position between the said one ends of these arms and the position at which they cross over, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the coupling being lifted.
 2. Lifting tongs according to claim 1, comprising two rectilinear guideways in said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways.
 3. Lifting tongs according to claim 2, comprising two arcuate guideways in said frame, and wherein the links are pivotally secured to the two arms through pins which protrude into the frame and are accommodated in the said arcuate guideways.
 4. Lifting tongs comprising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.
 5. Lifting tongs according to claim 4, comprising two sets of arcuate guideways in said frame, and a plurality of pins by which the second arms are pivotally secured (a) to the first arms and (b) to the crossed links, respectively, one set of guideways accommodating the pins effecting connection (a) and the other set of guideways accommodating the pins effecting connection (b), a further set of guideways defining said rectilinear path, and a pair of pins by which the crossed links are pivotally secured to the two jaws, the further set of guideways accommodating the said pair of pins.
 6. Lifting tongs comPrising a frame, a beam, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted, and locking means for automatically retaining the jaws of the tongs in an open posture after the beam has been lowered and the load set down.
 7. Lifting tongs according to claim 6, wherein the first arms are connected to said beam through a common pivot.
 8. A lifting tongs assembly comprising a framework, two sets of lifting tongs mounted on and spaced apart by said framework, and a beam common to the two sets of tongs, each one of said sets of tongs comprising a frame, a pair of first arms each connected at one end to said beam, a pair of second arms crossed over one another and each pivotally secured at one end to the frame and at their other ends to the other ends of the first arms, two crossed links pivotally secured at one end to each of the second arms at a position between the said one ends of these arms and their cross over position, and two jaws pivotally secured to the other ends of the crossed links and constrained by the frame to move along a common rectilinear path to grip a load between them in response to the beam being lifted.
 9. A lifting tongs assembly according to claim 8, comprising locking means secured to the beam, and including a pivotal hooked mechanism for automatically hooking around the framework after the beam has been lowered and the load set down whereby to constrain the jaws of the tongs to maintain their open posture, said mechanism being manually operable to unlock the jaws from their open posture.
 10. A lifting tongs assembly according to claim 9, wherein each set of tongs comprises two rectilinear guideways in the said frame, and wherein the links are pivotally secured to the jaws through pins which protrude into the frame and are accommodated in the said guideways. 